Re: Core Data modeling question
Re: Core Data modeling question
- Subject: Re: Core Data modeling question
- From: Jerry Krinock <email@hidden>
- Date: Fri, 28 Nov 2008 15:02:51 -0800
On 2008 Nov, 28, at 12:15, Markus Schneider wrote:
thanks for your advice. I will go with the relationships model.
Well, one more thing, and this is directed to others, not you Markus.
In a project I am working on, I too have an managed object Foo with a
property that is a set in my case a set of of strings. I have two
choices for modelling this property:
* model the set of strings directly as an attribute, of type
transformable
or
* model the set of strings as a a to-many relationship of 'bars' to
an entity Bar of class NSString.
The, latter, the "elegant" choice, does have a disadvantage when I
want to make a copy/insert a Foo from one managed object context into
a different managed object context.
If it's an attribute, it simply gets copied with all the other
attributes when I enumerate over -[NSEntityDescription
attributesByName].
But if it's a to-many relationship, I need to write and maintain
additional code in my -copy method. This additional code must
enumerate over the bars of the foo, copy/insert new Bars and wire up
the relationships.
So, I would say that the choice is indeed worth considering in each
application. Modelling as a to-many relationship is not always better
than modelling as an transformable attribute.
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